The traditional IP addressing model associates both an identity and a location of a device to a single IP address space. This results in mobility being a very cumbersome process, as identity and location are so tightly bundled. LISP is a routing architecture in which an identifier of a device, referred to as its Endpoint Identifier (“EID”), and its location, identified by its Routing Locator (“RLOC”), are split into two different name spaces. LISP also provides a dynamic mapping mechanism between the two address families. RLOCs remain associated with the topology and are reachable via traditional routing; however EIDs can change location dynamically and are reachable via different RLOCs, depending on where an EID attaches to the network. In a virtualized data center deployment, EIDs can be directly assigned to virtual machines (“VMs”) that are free to migrate between data center sites while preserving their IP addressing information.
LISP uses a dynamic tunneling encapsulation approach, rather than requiring the pre-configuration of tunnel endpoints. As previously noted, LISP name spaces include EID addresses, which include the IP address and previses identifying the endpoints, and RLOC addresses, which include the IP addresses and previses identifying the different routers in the network. EID reachability across LISP sites is achieved by resolving EID-to-RLOC mapping, while RLOC reachability is achieved by traditional routing methods. LISP sites may also include LISP site devices such as an Ingress Tunnel Router (“ITR”) and an Egress Tunnel Router (“ETR”). An ITR may comprise a LISP site edge device that receives packets from site-facing interfaces, or internal hosts, encapsulates the packets, and forwards them to remote LISP sites. The ITR may alternatively natively forward the packets to non-LISP sites. An ETR may comprise a LISP site edge device that receives packets from core-facing interfaces, or the transport infrastructure, decapsulates LISP packets, and delivers them to local EIDs at the site.